Generally, a wire take up apparatus which takes up a relatively thicker wire such as an electric wire or an electric cable on a reel in an arranged manner, comprises a distributor or traverser to distribute the wire along the axis of the reel. When the distributor reaches either of the flanges of the reel, it stops until a new winding layer starts and completes a first turn of the wire, and then it should be reversed in order to take up the subsequent turns of wire. Detector means which electrically detects raising up of the wire which is caused by a new winding layer starting on the old winding layer, has been disclosed by U.S. Pat. No. 3,257,087, for example. The wire raising up detectors disclosed by this patent are disposed adjacent to both flanges of a reel and each comprise a shoe to engage the wire wound on the reel so as to pivotally move about the axis normal to that of the reel, and a mercury switch mounted on the shoe. When the wire begins to be wound as a first turn of a new winding layer at either of the reel flanges, the shoe is tilted about the pivotal axis by raising up of the wire. Thus, the mercury switch is closed so that it produces an electric signal indicating raising up of the wire. One of the disadvantages of the prior art detector is that each time the outer diameter of the wire to be taken up varies, the mercury switch should be replaced by another having a tilted angle at which it is closed. Therefore, a particular mercury switch having a particular tilted angle at which it is closed, cannot detect raising up of the wires having various outer diameters. Another disadvantage of the prior art is that in case the reel flange is deformed without having a plane accurately normal to the axis of the reel, the detector cannot effectively detect raising up of the wire. Further disadvantage of the prior art is that the mercury switch which tends to be subject to impact due to engagement with the reel flange rotating at high speed, has an unstable operation, and that the detector tends to be injured due to the impact. Thus, with the prior art the wire cannot be taken up on the reel at the high speed.